ABC News and The Associated Press are reporting that law enforcement sources told them that surveillance cameras outside the Lord and Taylor department store captured the image of a man with a backpack, who is believed to have been involved in the attacks.

Those stories were eventually denied by FBI officials, but not before a crowd gathered outside the federal courthouse in Boston based on reports that a man was going to be arraigned.

The courthouse was later evacuated because of a bomb threat, officials said.

"This is going to take some time, a lot of time, particularly given there hasn’t been an individual that's claimed responsibility," said Gov. Deval Patrick.

Investigators said other evidence has been collected in the case, including the lid of one of the pressure cooker bombs that was reportedly found on a nearby roof. Officials said the pressure cooker was a Fagor brand, which is sold across the country.

Authorities also recovered a circuit board and what appeared to be batteries and wiring.

"The things we need from public are patience. Patience at a time when we are impatient for an answer," said Patrick.

The governor said the public needs to understand that not every piece of new information will be made public immediately to avoid compromising the investigation.

Meanwhile, a memorial to the victims of the bombing continues to grow on Boylston Street, not far from where the explosion happened.

President Barack Obama and first lady Michelle Obama are expected Thursday morning at the Cathedral of the Holy Cross, where they will gather with members of the community.

"We need vigilance, which is enormously important (for) people to keep an eye out for suspicious activity or parcels and let law enforcement know about that," said Patrick.